1. Field of the Invention
The present invention relates to the connection of tubulars for use in a wellbore. More particularly the invention relates to an apparatus and method for supporting and compensating a tubular during connection.
2. Description of the Related Art
In the construction and completion of oil and gas wells, a drilling rig is used to facilitate the insertion and removal of tubular strings into a wellbore. The tubular strings are constructed by inserting a tubular into a wellbore until only the upper end of the tubular is out of the wellbore. A gripping member close to the surface of the wellbore then grips the tubular that is in the wellbore. The tubular string's upper end typically has a threaded box end for connecting to the next tubular. The next tubular to be connected to the tubular string is then lifted over the wellbore center. The next tubular has a lower end with a pin end for threadedly connecting to the box end of the tubular string. As the next tubular is connected to the tubular string it is critical to not damage the threaded connections between the tubular string and the tubular.
In order to facilitate tubular connection compensators have been used to prevent damage to the threads. During make up of the connections compensators support the weight of the tubular being lowered to minimize the axial load transferred from the pin to the box during makeup. Historically compensators have been used in conjunction with single joint elevators. The compensator is located between a traveling block and the single joint elevator. Another elevator is provided that is capable of supporting the entire tubular string. With the tubular being held by the single joint elevator the tubular is aligned with the box of the tubular string. An operator standing on the rig floor then aligns the pin and the box. A power tong, and/or pipe spinner is then used to connect the box and pin ends to form a tubular string while the axial travel of the thread make up is compensated for by the compensator. The tubular string is then engaged and supported by the second elevator that is capable of supporting the entire tubular string. The gripping apparatus near the wellbore surface or spider then releases the tubular string. The second elevator lowers the tubular string toward the wellbore surface.
The weight of the single joint elevator and the equipment to connect the elevator to the traveling block is much greater than the weight of the tubular to be compensated. The percentage of the weight of the tubular is small compared to the entire weight that is compensated. This causes the compensators to be ineffective when compensating.
As the top of the tubular string nears the surface of the wellbore the operator on the rig floor removes the single joint elevator from the tubular string. The operator then moves the single joint elevator toward the next tubular to be installed. The next tubular's box end is brought up to the rig floor so that the single joint elevator may grip it. Once the tubular string has gone as low as it will go with the elevator, the spider is activated to grip the string. The main elevator is then unlatched from the string. With the single joint elevator engaging the next tubular and the main elevator free the traveling block is lifted. The next tubular is lifted into a vertical position over the well center. The next tubular is located over the well center and the connection process will start again.
Efforts have been made to reduce the manpower on drilling rigs in order to prevent injury, and damage caused by human error. It is known to use automated pipe handling equipment. Such equipment helps reduce the number of people. The pipe handling equipment includes an arm or set of arms for grabbing a tubular to be installed from a rack and moves the tubular substantially over the well center for connection. The pipe handling equipment has very limited compensation capabilities. Thus, often times the insufficient compensation capabilities of the pipe handling equipment will damage the connections while handling the tubulars. This is especially true when using easily damaged tubulars such as chrome tubulars. The tubulars are then connected using power tong or pipe spinners in conjunction with the pipe handling system.
There is a need for enhanced compensation in combination with a traveling member. There is a further need to adapt the compensation for quick connection to a top drive or traveling block. There is yet a further need for a compensation system used in conjunction with a pipe handling system.